Riemerellosis, contagious disease of domestic ducks in Korea, occurred in December of 2007 in a farm located in Eumsung, Chungbuk province. The affected ducks were 22 days old and the owner reported that almost one hundred of ducks had died everyday for a few days after infection. Clinical signs were listlessness, ocular and nasal discharge, greenish diarrhea, ataxia, tremor of head and legs, and coma. On necropsy we found fibrinous exudate, which involved serosal surfaces in general, but most evidences were in the pericardial cavity and over the surface of the liver. The causative agent was isolated from the liver of the affected ducks and identified as Riemerella anatipestifer using biochemical tests. Also, the isolate was susceptible to ampicillin, cephalothin, sulfamethazole/trimethoprim, Florfenicol among the 23 species antibiotics (AST Discs, OXOID) used in our laboratory. Further studies should be needed for the more effective control and better epidemiological information such as pathogenicity, serotype, genotype and treatment.